1. Field of the Invention
The present invention relates to a device and method for caching control, and a computer product that allocate a cache memory appropriately to a storage device, and execute data caching efficiently.
2. Description of the Related Art
A small computer systems interface (SCSI) command used between a storage device such as a hard disk device and a computer is transmitted via the Internet Protocol (IP) network, thereby enabling plural computers to access the storage device connected to the IP network. This technique, known as small computer systems interface over IP (iSCSI), has recently become popular.
Specifically, according to the iSCSI technique, the computer can access the storage device via the IP network by transmitting the SCSI command encapsulated in a transmission frame of the Transmission Control Protocol/Internet Protocol (TCP/IP) packet.
Based on the above arrangement, an application program that uses the storage device can access the storage device according to the conventional method, via the IP network for high-speed communications, without recognizing the existence of the iSCSI (see, “Latest IP storage technology “iSCSI”” Naotaka AOKI, [online], Oct. 5, 2002, ITmedia, [searched on Mar. 7, 2005], Internet <URL: http://www.atmarkit.co.jp/fnetwork/tokusyuu/16iscsi/iscsi01.html>).
According to the above conventional technique, when the application program uses the storage device, a memory of the computer that manages the storage device is allocated to the storage device as a cache memory. However, it is difficult to appropriately allocate the capacity of the cache memory.
For example, when the cache memory is allocated to the storage device to meet maximum access to the storage device by the application program, the allocated cache memory is not used when the application program is not using the storage device, and this is a waste of memory.
Particularly, when a time zone during which the access from an application program to the storage device is concentrated is different for each application program, it becomes more difficult to appropriately allocate the capacity of the cache memory.
Therefore, the way of appropriately allocating the cache memory to the storage device and the way of efficiently caching data stored in the storage device are important.